UV light is electromagnetic radiation having a wavelength between about 250 nm and about 400 nm. A number of organic compounds are decomposed or degraded by exposure to the UV light.
Then, a wide variety of UV light absorbers are generally incorporated into the commercial organic products such as polymeric materials (e.g. natural or synthetic resin and rubber), dyes, cosmetic creams and the like to prevent the degradation of the product such as discoloration, the suntan of skin, and the like.
In recent years, the UV light absorbers are incorporated into the heat-sensitive materials widely used as heat-sensitive transfer recording materials for recording devices such as facsimiles and printers to improve the light-resistance of the heat-sensitive transfer recording materials. The UV light absorbers may also be incorporated into the liquid crystal material widely used as display materials for watches and electric calculators, meters for cars, and the like. Furthermore, there is a proposal of the method for improving the light-resistance of the color photographic image using a UV light absorber containing transparent film. Wherein, the transparent film is superimposed onto the printed surface of the photograph as a protective UV filter layer.
Examples of the conventional UV light absorbers include salicylates, benzophenones, benzotriazoles, cyanoacrylates and hindered amines. Since much of the compounds are substantially colorless, the incorporation of the UV light absorbers into the products does not affect a transparency or a color of the products.
Most of these conventional UV light absorbers, however, absorb the UV light of the wavelength ranging between about 290 nm and about 380 nm. There have been no conventional appropriate UV light absorbers which exhibits effective absorptivity in the spectral area ranging between about 380 nm and about 400 nm.